Understanding Fertilization and Embryonic Development
Fertilization and Embryonic Development
Fertilization is a chemical process by which the sperm penetrates the egg. There are two types of fertilization: internal and external.
- Internal fertilization occurs when sexual intercourse takes place. In this case, millions of sperm are expelled and enter the vagina.
- External fertilization occurs when sperm swim in the water to fertilize the eggs released by the female.
Segmentation
During this stage, the zygote undergoes a number of divisions that produce large
Read MoreNervous System and Sensory Organs: Structure, Function, and Disorders
Cells of the Nervous System
The nervous system is formed by very distinct cells. Neurons are the cells responsible for conducting nerve impulses. Neurons communicate by connecting the axon with the dendrites.
Types of Neurons
- Sensory or afferent neurons
- Interneurons or association neurons
- Motor neurons
Sensory Receptors
Receptors are a set of specialized cells that perceive stimuli. According to the stimulus, they are classified as:
- Thermoreceptors
- Chemoreceptors
- Mechanoreceptors
- Photoreceptors
Internal receptors
Read MoreAnimal Kingdom: Characteristics of Major Phyla
Phylum Porifera
Phylum Porifera, consisting of 5,500 species, are the simplest animals that exist and are sessile. Their bodies are pierced by pores that communicate with the gastrocele, covered by choanocytes. They have radial symmetry and their skeletons consist of spicules. Examples: Sponges.
Phylum Cnidaria
Phylum Cnidaria, with 10,000 species, are lower animals with more differentiated tissues. They are shaped like a polyp (sessile sack) or jellyfish (free-floating). The surface of their bodies
Read MoreCell Components and Their Functions
Cell Organelles: Structure and Function
1. Plasma Membrane (Cell Membrane)
Structure: A bilipid membranous layer composed of proteins and carbohydrates. It is fluid-like.
Function: The cell membrane separates the cell from its external environment and is selectively permeable, controlling what gets in and out. It protects the cell and provides stability. Proteins are found embedded within the plasma membrane, with some extending all the way through in order to transport materials. Carbohydrates are
Read MoreCellular Structures and the Circulatory System
Cellular Organization and Function
The cell is the basic unit of living matter. Depending on their structure and organization, cells are classified into different types of living organisms.
Prokaryotic Cells
Prokaryotic cells lack a distinct nucleus; their genetic material is located freely in the cytoplasm, along with the enzymes necessary for their maintenance and reproduction.
Eukaryotic Cells
Eukaryotic cells possess a distinct nucleus, where the genetic material is enclosed by a membrane, separating
Read MoreUnderstanding Ecology: Habitats, Ecosystems, and Biotic Factors
Ecology is the science that studies the relationships and networks of interdependencies between living beings and the environment in which they live.
What is the Environment?
The environment of a being is formed by the combination of living (biotic) and nonliving (abiotic) elements that surround them.
Defining Habitat
A habitat is the ideal place for an organism, and is inhabited by mainly ideal conditions to live and reproduce.
Biotope Explained
The biotope consists of non-living elements. It is a particular
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